This invention pertains to concrete and cement additive compositions, known as air-entraining admixtures, for incorporation in hydraulic cement mixes, such as portland cement concretes and mortars, but not limited thereto, for the purpose of increasing the durability in the hardened state of such mixes, to freeze-thaw cycles under conditions of water saturation. The increased durability of the cementitious mix under such conditions is the result of the development in the plastic portland cement mix of a system of air bubbles that will remain in the mix after hardening and meet the specifications of resistance to freezing and thawing stipulated in ASTM designation C-260. This requires that the air void system be a specified amount as volume percent of the hardened cementitious mass, and that it have bubbles within a specified range of sizes and spacing parameters as designated by ASTM specification C-457. It is well known in the art that in order to meet these requirements, it is necessary to use surface active agents or surfactants to obtain the desired amount of air entrainment.
There are a number of chemical agents to achieve the specified air entrainment system. Generally, these are organic chemicals which are broadly classified as soaps and detergents. One of the best known chemical agents of this type is known in the art as Vinsol resin, which is a wood resin salt and is the standard against which other air-entraining agents are tested under ASTM specification No. C-233. Vinsol resin is normally employed as an aqueous alkaline solution that is added to a plastic, cementitious mix, either alone or in combination with other chemical admixtures. In the latter case, the Vinsol resin solution is added separately because of its chemical incompatibility with many other admixtures, due to the fact that the pH and the presence of calcium and various other ions renders insoluble the alkali-neutralized acids comprising Vinsol resin.
It is also known in the prior art to use a variety of surfactants, both anionic and nonionic, in the broad class of detergents to obtain a desirable degree of air entrainment in cement, mortar and concrete. Often these are used in various combinations. Some of these surfactants are sulfated ester ammonium salts of higher primary alcohols (or additional products with ethylene oxide), alkylbenzenesulfonic acid salts, salts of petroleum acids, fatty acids and proteinaceous substances, and organic salts of sulfonated hydrocarbons.
For example, U.S. Pat. No. 4,249,948 disclosed the use of an alpha olefin sulfonate with a water reducing agent wherein the former acts as an air-entraining agent in a hydraulic cement composition. U.S. Pat. No. 4,046,582 disclosed the use of a higher secondary alcohol oxyalkylene sulfate as an air-entraining agent. PCT International Application No. WO 85/01,500 (U.S. patent application Ser. No. 537,185; filed 9-29-83) discloses the use of a multicomponent air-entraining additive for hydraulic cement mixes which comprises a three-component mixture of an alkylarylsulfonic acid salt, an alkanolamine salt of a fatty acid such as tall oil, and a nonionic component selected from polyethylene glycol derivatives and diethanolamine adducts of cocamide derived from coconut oil.
However, these air-entraining additives are not entirely satisfactory with respect to the stability of the air bubbles in concrete, the ability to perform in the presence of fly ash in the mix, the effect on improving the workability of the concrete, the need to use higher dosages of admixtures known in the art, or tendencies to either lose air or to uncontrollably increase air content, as mixing time is extended. Loss of workability is measured by the slump cone in accordance with the American Society for Testing and Materials (ASTM) designation C-143. The biggest disadvantage is the reduction in compressive strengths by as much as 5% strength loss per 1% increase of entrained air. This loss is due, in part, to an irregular bubble sizing and the coalescence of bubbles in the mix causing larger voids, thus reducing the compressive strengths.
In portland cement concrete, sands vary in fineness from 2.2 to 3.5 fineness modulus, which is an empirical figure to determine coarseness of sand. The higher the fineness modulus (FM), the coarser the sand. It is well known that as the sand varies, plus or minus, from 2.7, it becomes increasingly difficult to entrain air in the portland cement concrete. When sands arrive at the range of an FM of 3.3, large doses of air entrainment additive are necessary to control the air.
Thus, there exists the continuing need to discover new and improved air-entraining agents, especially ones that will overcome the problems described above.